Process for the manufacture of hypochlorite bleaching compositions

Abstract

PCT No. PCT/US96/05603 Sec. 371 Date Nov. 17, 1997 Sec. 102(e) Date Nov. 17, 1997 PCT Filed Apr. 19, 1996 PCT Pub. No. WO96/36560 PCT Pub. Date Nov. 21, 1996The present invention discloses a process for the manufacture of liquid aqueous bleaching compositions comprising alkali metal hypochlorite, a strong source of alkalinity and water; said process comprising the steps of: mixing alkali metal hypochlorite, strong source of alkalinity and said water, separating the insoluble species formed in the first step, and thereafter adding a chelating agent capable of chelating heavy metal ions. The compositions provided by the process according to the present invention are substantially free of heavy metal ions, thereby providing improved whiteness performance and/or fabric safety performance.

We claim: 
     
       1. A process for the manufacture of an aqueous liquid bleaching composition having a pH of from 10 to 14 and comprising an alkali metal hypochlorite, a strong source of alkalinity and water, said process including the steps of: 1) mixing in a first step said alkali metal hypochlorite, said strong source of alkalinity and said water,   2) separating in a second step the insoluble species formed in said first step, and   3) thereafter adding a chelating agent capable of chelating heavy metal ions, wherein said chelating agent is a polycarboxylic acid of pyridine or salts thereof having one of the following formulas: ##STR2## in which R is hydrogen, a halogen atom, a hydroxyl group, an amino group, a carboxylic group, or a short-chain alkyl group (C1-C4), and n is 1 or 2 or mixtures thereof.   
     
     
       2. A process according to claim 1 wherein said chelating agent has a binding constant K to heavy metal ions defined as follows, or mixtures thereof: when n=1, then K>10 5 ,   when n=2, then K>10 6 ,   when n=3, then K>10 7 , wherein n is the number of chelating agent molecules per heavy metal ion and wherein K is=(MLn)/(M)(L)n and (MLn) is the concentration of heavy metal ion/chelating agent complexes, (M) is the concentration of free heavy metal ions, (L) is the concentration of free chelating agents.     
     
     
       3. A process according to claim 1 wherein said chelating agent has a binding constant K to heavy metal ions defined as follows, or mixtures thereof: when n=1, then K>5.10 5 ,   when n=2, then K>5.10 6 ,   when n=3, then K>5.10 7 , wherein n is the number of chelating agent molecules per heavy metal ion and wherein K is=(MLn)/(M)(L) n  and (MLn) is the concentration of heavy metal ion/chelating agent complexes, (M) is the concentration of free heavy metal ions, (L) is the concentration of free chelating agents.     
     
     
       4. A process according to claim 1 wherein said chelating agent, or mixtures thereof, is added in amounts of from about 0.01% to about 5% by weight of the total composition. 
     
     
       5. A process according to claim 1 wherein said chelating agent, or mixtures thereof, is added in amounts of from about 0.01% to about 3% by weight of the total composition. 
     
     
       6. A process according to claim 1 wherein a precipitating agent which binds to heavy metal ions forming thereby salts having a solubility product in water not higher than about 10 -6  at a temperature of about 25° C., is added to said composition before the separation step. 
     
     
       7. A process according to claim 1 wherein a precipitating agent is added to said composition before said separation step, said precipitating agent being selected from the group consisting of sodium oxalate, sodium phosphonate, sodium borate, sodium sesquicarbonate, sodium selenure, sodium vanadate, sodium tellurure, sodium thiocarbonate, sodium polonure, sodium carbonate, sodium silicate, and mixtures thereof. 
     
     
       8. A process according to claim 1 wherein a precipitating agent is added to said composition before said separation step, said precipitating agent being selected from the group consisting of alkali metal salts of oxalate, phosphonate, borate, sesquicarbonate, silicate, carbonate, selenure, vanadate, tellurure, thiocarbonate, polonure, and mixtures thereof. 
     
     
       9. A process according to claim 7 wherein each precipitating agent present is added in an amount of from about 0.01% to about 10% by weight of the total composition. 
     
     
       10. A process according to claim 7 wherein each precipitating agent present is added in an amount of from about 0.01% to about 7% by weight of the total composition. 
     
     
       11. A process according to claim 7 wherein said composition comprises from about 0.1% to about 10% by weight of the total composition, based on active chlorine, of hypochlorite. 
     
     
       12. A process according to claim 7 wherein said strong source of alkalinity is an alkali metal hydroxide, preferably sodium hydroxide, and wherein the pH is from about 11 to about 14. 
     
     
       13. A process according to claim 7 wherein the insoluble species formed are separated from said composition by filtering said composition with a decantation filter. 
     
     
       14. A process for the manufacture of an aqueous liquid bleaching composition having a pH of from about 10 to about 14 and comprising from about 0.01% to about 10% by weight of the total composition, based on active chlorine, of hypochlorite, a strong source of alkalinity and water, said process including the steps of: mixing said hypochlorite, said strong source of alkalinity and said water,   adding a precipitating agent selected from the group consisting of alkali metal salts of oxalate, phosphonate, borate, sesquicarbonate, silicate, carbonate, selenure, vanadate, tellurure, thiocarbonate, polonure, and mixtures thereof;   separating the insoluble species formed from said composition,   and thereafter adding a chelating agent having a binding constant K to heavy metal ions defined as follows, or mixtures thereof: when n=1, then K>10 5 ,   when n=2, then K>10 6 ,   when n=3, then K>10 7 , wherein n is the number of chelating agent molecules per heavy metal ion and wherein K is=(MLn)/(M)(L) n  and (MLn) is the concentration of heavy metal ion/chelating agent complexes, (M) is the concentration of free heavy metal ions, (L) is the concentration of free chelating agents.       
     
     
       15. A process according to claim 14 wherein the steps of said process each precipitating agent present is added in the amounts of from about 0.01% to about 10% by weight of the composition. 
     
     
       16. A process according to claim 15 wherein the steps of said process (L) is in the concentration of free chelating agents in amounts of from about 0.01% to about 5% by weight of the total composition.